[ChromeDriver] Add acceptInsecureCerts capability for headless.

Implemented using a new DevTools method to override certificate
error handling browser-wide. This allows ignoring certificate
errors in headless mode, too.

Bug: 721739
Change-Id: I99d1962147ae638ef83dad5cad6fe1311e7c98b1
Reviewed-on: https://chromium-review.googlesource.com/810790
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#525318}
14 files changed